I. Field
The subject technology relates generally to communications systems and methods, and more particularly to systems and methods for performing efficient communications handoff between access terminals and nodes in an access network.
II. Background
Communication systems are widely deployed to provide various communication services such as voice, packet data, and so on. These systems may be time, frequency, and/or code division multiple-access systems capable of supporting communication with multiple users simultaneously by sharing the available system resources. Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Multiple-Carrier CDMA (MC-CDMA), Wideband CDMA (W-CDMA), High-Speed Downlink Packet Access (HSDPA), Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, and Orthogonal Frequency Division Multiple Access (OFDMA) systems.
A communication system may employ a handoff scheme to allow a moving Access Terminal to stay in communication with serving access points or sectors via Forward Link (FL) and Reverse Link (RL) mechanisms. The sector from which data transmissions are received is referred to as the FL serving sector, and the sector to which the AT sends data transmissions is referred to as the RL serving sector. One objective of fast switching or handoff is to not introduce any packet loss at the higher layers while allowing for uninterrupted transmission to the access terminal. A second objective is to minimize the backhaul communication required between the AP's in the active set. In general, there is a trade off between the amount of back haul communication required and the handoff latencies that can be achieved.
In order to continue uninterrupted data transmission, the new serving sector needs to determine the forward looking RLP state for the forward link, where the forward looking RLP state is defined as the data received at the anchor AP and not yet transmitted, and the data that needs to be retransmitted based on Receiver Status messages from the access terminal. This RLP state is transferred to the new serving sector as part of an L2 handoff negotiation. There is a need for techniques to efficiently select reverse-link (RL) and/or forward-link (FL) serving sectors and indicate such choices for efficient RL and/or FL handoffs in a communication system. More particularly, current systems do not effectively utilize information that the AN may have accumulated when performing a handoff nor do current techniques provides methods for effectively communicating such information that may lead to improved communications performance.